Ethanolamines were first synthesized in a laboratory setting in 1860 when the pioneering Alsatian chemist Charles-Adolphe Wurtz heated ethylene chlorohydrin with aqueous ammonia in a closed tube. While never commercially interesting during the nineteenth century, ethanolamines were nonetheless enough of a technical curiosity that they attracted considerable technical interest. For example, the great German chemist Ludwig Knorr significantly improved upon Wurtz's work when in 1897 he successfully separated ethanolamines into their mono-, di- and triethanolamine component parts, as well as made other contributions to their synthesis.
Despite process improvements and continued laboratory interest, ethanolamines only attracted substantial commercial development after 1945. At this time, the significant increase in the industrial production of ethylene oxide was also leading to considerable interest in ethylene oxide derivatives. Ironically, this commercial movement from ethylene oxide to ethanolamines recapitulated the history of the synthesis of the chemicals as Wurtz's synthesis of ethanolamines in 1860 was largely the result of his trying to figure out what he could make with a new chemical he had discovered just the year before—ethylene oxide.
In the post-war years, significant process improvements were subsequently made as a result of the burgeoning interest in ethanolamines, which had proven to be extremely versatile intermediates in a wide variety of chemical products such as emulsifiers, surfactants, and agrichemicals, as well as many others. Examples of such improvement can be seen in, for example, U.S. Pat. No. 2,196,554 to Guinot which discloses an aqueous process with an improved heat integration and efficiency scheme for the concentration of ethanolamines in the process backend. Another example is GB Patent No. 760,215 to Lowe et al., which discloses that by controlling the molar ratios at which ammonia and ethylene oxide are mixed, then a higher content of di- or tri-ethanolamine may be obtained. Alternatively, GB Patent No. 1 529 193 to Gleich discloses that a higher di- or tri-ethanolamine content may be obtained by recycling di- or tri-ethanolamine to the reactor.
Given that the conversion of reactants to products is nearly complete in an ethanolamines process and the fact that the process has developed into a mature technology by process improvements such as those mentioned above, wringing out additional improvements or competitive technical advantages in ethanolamines technology has proved difficult.
Accordingly, there is a continuing need in the art for an ethanolamine manufacturing process with the improved process economics and efficiency of operating at high ammonia to water ratios and that also produces quality, on-spec product.